Fluid ejection devices may find uses in a variety of different technologies. For example, some printing devices, such as printers, copiers and fax machines, print by ejecting tiny droplets of a printing fluid from an array of fluid ejection orifices onto the printing medium. The fluid ejection mechanisms are typically formed on a fluid ejection head that is movably coupled to the body of the printing device. Careful control of such factors as the individual fluid ejection mechanisms, the movement of the fluid ejection head across the printing medium, and the movement of the medium through the device allows a desired image to be formed on the medium.
Some fluid ejection devices may be configured to eject a plurality of different fluids, such as different ink colors and/or compositions, from a single fluid ejection head. In such a fluid ejection head, each individual fluid is typically ejected from a group of closely spaced fluid ejection orifices, and the different groups of orifices for the different fluids are spaced a greater distance apart. The use of such a fluid ejection head may offer several advantages over the use of separate fluid ejection heads for each different fluid. For example, a single, fluid ejection head is typically less expensive than multiple fluid ejection heads, and also may use less space than multiple fluid ejection heads for a fluid ejection device of a comparable size.
While the use of a single fluid ejection head to eject a plurality of different fluids may offer advantages over the use of multiple fluid ejection heads, such a fluid ejection head may also present various problems. For example, when printing with (or otherwise using) any fluid ejection device, small droplets of fluids may end up on the surface of the fluid ejection head surrounding the orifice from which it was ejected, instead of onto the intended medium. Where the fluid ejection head is configured to eject multiple fluids, these stray droplets may contaminate an adjacent fluid ejection orifice for a different fluid, and thus cause undesirable mixing of fluids.
Also, many fluid ejection devices include a wiper structure to clean the fluid ejection head of stray fluid droplets. Typically, the wiper structure wipes across the fluid ejection head surface, pushing a wave of fluid or fluids in front of it. Depending upon the separation of the different fluid ejection orifices, the size of the fluid ejection head, and the configuration and direction of movement of the wiper structure, the wiper structure may mix the different fluids, and thus may cause the contamination of fluid ejection orifices of one type of fluid with other fluids.
The mixing of fluids may cause problems with color reproduction, and may cause other problems as well. For example, some fluids commonly used with fluid ejection devices are configured to react with other fluids ejected from the same device. Inks with this property are referred to generally as xe2x80x9creactive inks.xe2x80x9d If one of the reacting fluids is not an ink, it may be referred to as a xe2x80x9cfixer fluid.xe2x80x9d Where two reactive fluids are ejected from the same fluid ejection device, the fluids may be configured to immediately harden at the boundary where the drop of one fluid meets a drop of the other fluid to prevent color mixing and/or bleeding on a fluid-receiving medium. Thus, where one reactive fluid contaminates the ejection orifices of a different reactive fluid, the fluids may harden and clog the ejection orifice. The hardened fluids may then be difficult to remove by xe2x80x9cspittingxe2x80x9d, or firing fluids through the orifice at a cleaning station.
These problems may be somewhat reduced by increasing the size of the fluid ejection head, and spreading the fluid ejection orifices for each fluid farther away from orifices of other fluids. However, this may increase the cost and size of the fluid ejection device, and thus may negate some of the advantages of the use of a single fluid ejection head to eject multiple fluids.
Some embodiments of the present invention provide a fluid ejection head, wherein the fluid ejection head includes an orifice layer disposed on top of a substrate layer. The fluid ejection head also includes a first group of fluid ejection orifices and a second group of fluid ejection orifices formed in the fluid ejection head, wherein the first group of fluid ejection orifices and the second group of fluid ejection orifices are configured to eject two different fluids, and an elongate channel formed in the fluid ejection head, wherein the channel is positioned between the first group of fluid ejection orifices and the second group of fluid ejection orifices in such a location as to inhibit cross-contamination of fluids ejected from the first group of fluid ejection orifices and second group of fluid ejection orifices.